Hempcrete: breaking away from the norm

by Beck Rodgers from Building Ideology

Australians like to build with brick.  Hempcrete however is making its way into the Australian market allowing people the choice to move away from this norm, and create healthier homes.  With a lower embodied energy than brick and with great insulating qualities it should not be overlooked.

As a building biologist, I look at the interaction of people and buildings and educate people to understand that health hazards can exist in their homes, and how ignoring these hazards may have an adverse impact on their health. Our homes should be considered as our third skin (our clothes being the second), so it is important that they help provide us with an environment which is beneficial to our health and wellbeing.

I believe that every home is as individual as the people that live in it and they should be treated as such.  However, we tend to use standard building designs and manufactured components that fit together to build a home and just plonk them onto a site. In addition, energy efficiency through vapour barriers and thermal insulation, tighter building skins and the reliance on mechanical devices to maintain air comfort (temperature and humidity) levels lead to the continual creation of the sick building situation we are beginning to suffer from today. This way of building has created an indoor air mass that can be more polluted than the exterior air in industrial cities.  

When building our homes, most people would agree that in Australia, we use brick.  This is because it’s a norm - cultural product which represents a person’s basic knowledge of what others do and what they think they should do.  

How and why did it become a norm?  Especially in the Perth metropolitan area where double brick homes are very popular. According to the Australian Bureau of Statistics, the use of brick has increased throughout Australia.  In 1911, 25% of homes had walls made of brick, increasing to 71% in 1999. Between 1993 and 1994, 87% of new homes built in Western Australia had outer walls of double brick versus 1% in Victoria and the Australian Capital Territory.  New dwellings of single brick were highest in Australian Capital Territory (97%), South Australia (88%) and Victoria (86%).

There are a few reasons why there was an increase in the use of brick, especially in the Perth metropolitan area.  Firstly, Midland Brick came on the scene after World War II to overcome the shortage of building materials.  They capitalised on the good quality, abundant supply of clay in the Perth area and the cheap transport costs of moving bricks from their plant in Midland to building sites, by advertising heavily to the local population that brick houses are safer and better.  Secondly, most areas in the Perth area have sandy soils, which are easy to compact.  In areas of Perth with more clay based soils, such as the hills, frame constructions are more common.  Thirdly, the perception exists that if a house is not made of double brick it is not as structurally sound as a lightweight-framed house and the re-sale value of double brick homes are higher.  These views have been promoted over the years by the brick manufactures, real estate agents and builders, with some builders actually refusing to build anything other than double brick.  Some builders have created construction teams structured around double brick, making it easier to source materials and subcontractors, ultimately offering a reduced cost incentive to the buyer.

As a building biologist, I don’t have an issue with bricks as a building material. They are pretty good in comparison.  However, there are other choices of building materials, that are often overlooked because of this norm.   When choosing building materials, we want to choose those that minimize embodied energy and avoid toxic materials that may be detrimental to health or the environment during its manufacture and construction.

Hempcrete is a concrete building material emerging in Australia. After researching and rating both Hempcrete and brick, Hempcrete has rated a score of 40.5 with brick coming in at 32 (which is still good).

Clay bricks provide:

  • thermal mass & insulation (however additional insulation is required)

  • strength and durability,

  • fire resistance.

  • low maintenance, and will not harbor vermin,

  • offer exceptional sound insulation qualities, particularly for low frequency noise.

  • inert, non-toxic and do not off gas volatile organic compounds into the indoor air mass

  • some hygroscopic properties

The overall embodied energy of clay bricks is considered to be around 2.5MJ/kg.  Brick manufacturing creates polluting emissions, mainly particulate matter.  They use raw materials obtained from rock and oil which may contain various amounts of naturally occurring radioactive nuclides.  Bricks are usually installed manually with brick walls often considered to have a lifespan of over 100 years.  Most brick walls require little maintenance with some re-pointing of mortar joints required after 25 years.  Bricks are also recyclable, after demolition of a home around 75% can be reused.

Much of Hempcrete’s properties come from its construction.  Hempcrete:

  • is porous allowing the material to retain heat, requiring less energy for a building to maintain a stable temperature

  • is an excellent insulator and does not require additional insulation,

  • has excellent hygroscopic properties assisting in regulating the indoor humidity

  • will not crack severely under movement and is three times more resistant to earthquakes than regular concrete

  • is durable and fire resistant

  • is naturally termite, pest and mould resistant, due to the use of lime  

  • is non-toxic and will not off gas volatile organic compounds into the indoor air  

  • has good acoustic properties.

  • can easily be designed to create different shapes and can be formed for precise openings for windows and doors, allowing water tight sealing to be installed.  

Hempcrete should be considered as an alternative to clay bricks as it has a much lower embodied energy.  The embodied energy of hemp has been calculated to be around 1.4MJ/tonne.

The hemp shiv is grown without the use of chemicals, fertilisers and pesticides and is a fast growing, hardy crop, and is becoming a good farming choice for Australian farmers.  Hemp crops are great for land that has become unusable as they will rejuvenate poor soils and has even been demonstrated to remove heavy metals from soils while remaining free of the metals itself.  Plus, the production of hemp can contribute to reductions in atmospheric carbon.  The lime binders may have some cementitious or pozzoloaic materials or other additives added which may be naturally occurring or be by-products of other processes. Hempcrete must be given time to dry out properly to prevent moisture problems occuring inside the home.  Although it takes some time to dry out completely, over time the lime will grow harder and turn back into rock petrifying completely meaning a wall of Hempcrete could last thousands of years.  Additionally, the product can be recycled and reused, without huge energy requirements.  

We all deserve to live in healthy environments.  Hempcrete is a good choice of building material for your home.  Break away from the norm that the brick suppliers, builders and real estate agents have created and consider this material when building your new home.  It gets a thumbs up from me.

If you need further information or assistance with choosing healthy materials or the design of your new home, we offer healthy building design and advice - http://www.buildingideology.com.au/index.php/healthy-building-design-advice/


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